Log Message:
spdlog: update to 1.8.1.

1.8.1

    Fixed load_env_levels() and load_argv_levels() #1680 (thanks @Tridacnid ).
    Fixed stdout sink that produced extra carriage returns on Windows #1675 \ 
(thanks @chris-t-w ).
    Fixed msvc_sink including windows.h #1667 (thanks @Ryan-rsm-McKenzie).
    Fixed stopwatch's clock to use chrono::steady_clock #1676 (thanks @SuperWig).
    Added support for Rcpp (R cpp compiler) #1685 (thanks @eddelbuettel).

1.8.0

    Upgraded bundled fmt to version 7.0.3.
    New stopwatch utility for quick & easy logging of elapsed time.
    Raised CMake requirement to 3.10 and cleanup CMakeLists.txt (#1624). Thanks \ 
@tambry.
    Added get_level() and should_log() functions to the spdlog:: namespace \ 
(#1628). Thanks @eyalroz.
    Fixed tcp_client for macOS (#1640). Thanks @dkruempe.
    Fixed cfg::load_env_levels() function declaration (#1651). Thanks @bareya.
    Updated Fedora install info in the readme (#1653). Thanks @gk6k6k.
    Fixed #1617 (aligned function pattern flag is broken). Thanks @VelocityRa \ 
for reporting.
    Fixed #1581 (compiling under msys in win10).